southeaster

Thanks for all the comments. These disks are laser cut. I used to use waterjet cutting but the prices seem to go up and up so I switched to a laser cutting place that worked out MUCH cheaper. Very interesting to hear about the heat from waterjet cutting! Did that mean it made clouds of steam? The application is for wind turbines - see my site Wind power generator and alternative energy - small scale homemade turbines. I would be happy with 0.5mm tolerance. Better than that would be good! Less than 0.1mm is irrelevant.

Report back: I left them on a three ring gas ring for about 20mins. It got very hot - but not glowing at all. Then into a sand bath, and about an hour later removed it - no change. Next I tried a high flow blowtorch (LPG), but after 15min or so I could see I was not going to get it to glow. Into the sand anyway, and no change after it had cooled. So a friend who has access to a press has taken the plates and will try and bend them straight(er). I will report back once that is done...

Thank you for sharing your expertise! The plates were laser cut, from rolled mild steel plate. So I guess the warping came from edge shrinkage. I don't have a rosebud head, so perhaps I could use my high flow LPG torch? And could the gas ring be used before hand to get the temperature up a bit? I am nervous to hammer the disk - it is a rotor which needs to be flat and spin true, and I would be worried hammering would distort the surface. The sand bath sounds simple - medium red heat, and leave it to be. I think I will try that first. The wet rag also sounds good, but seems like it requires much more skill and judgement. I will try that next if the sand bath doesn't help. Thanks again to all of you.

Hello, I have a problem I hope you experts can help me with. I have had 250mm diameter disks cut from 6mm mild steel plate. Some of them are warped, and I have heard that heating the plate can 'destress' it and cause it to pull flat. Is that true? And if so, to what temperature does it need to get to? Could I do it by heating over a gas ring?